1. Field of the Invention
The present invention relates to a diagnostic device for a field bus which outputs diagnostic information and parameters, as well as certain information about peripheral properties, to a display instrument for display and evaluation.
2. Description of the Prior Art
As the use of field bus systems in control systems becomes more and more widespread, the importance of tools for the rational commissioning and maintenance of such field bus systems is constantly growing. A diagnostic device for a field bus is known from the technical article published in “Elektronik Praxis, issue 23, pp. 108–110”. The diagnostic device described therein fulfils the object of providing diagnostic data for a field bus in the form of a clear text message or a visual display, as a histogram for example, for long-term analyses. In terms of content, the display provides visual identification of fault locations in the event of sporadic transmission errors, monitoring quality in fibre optic lines and messages from bus modules regarding faults on associated peripherals.
However, the critical disadvantage of this device is that the logical and physical connection between the field bus switching component and the diagnostic device is assured via a purpose-designed interface connection between the field bus switching component and the computer with diagnostic device, such as Ethernet or V24.
A visualization system is known from DE 299 13 057 U1, in which the logical and physical connection between the programmable logic controller PLC and a visualization application is assured by an interface provided for that purpose (for example V24 or Ethernet). For additional field bus switching components connected to the PLC, the interface that is located in the field bus switch must be used to transmit the diagnostic data contained in the field bus switch. It is not possible for the diagnostic information contained in the PLC to be transferred to the diagnostic device.
The standardized software interface for ActiveX components is known from “Inside OLE Second Edition, Kraig Brockschmidt, Microsoft Press, 1985” and “ActiveX Controls Inside Out, Adam Denning, Microsoft Press, 1987”.
“Elektro Automation, 3/2001, Page 32”, includes a description and illustration of the typical data communication mechanism for a diagnostic device for a field bus. In this case, programming effort is required within the control unit in order to transfer the data in the control unit to a diagnostic device. To avoid costly programming activities, the diagnostic device is integrated in a visualization application as an ActiveX software component. Since the transmission path of the diagnostic data from the field bus to the diagnostic devices no longer passes through the controller, an additional interface connection is required therefor.
A diagnostic device in a process controlling system is known from DE 100 08 020 A1. In this case, however, only measurement and control variables from the application are monitored, and a fault is output to the display or action is initiated. The diagnostic device in DE 100 08 020 A1 is a constituent part of the control device, since the performance of the control program is influenced by the diagnostic device. The diagnostic device described has the critical disadvantage that it does not monitor the functioning of a field bus or process control network.